Wind Calculation System Using a Constant Bank Angle Turn

ABSTRACT

A method and apparatus for operating an aircraft. The aircraft is flown at a constant bank angle in which the aircraft crosses an intended ground track for the aircraft. Information is identified about a wind using positions of the aircraft flying at the constant bank angle.

BACKGROUND INFORMATION

1. Field

The present disclosure relates generally to aircraft and, in particular,to operating unmanned aerial vehicles (UAVs). Still more particularly,the present disclosure relates to the automatic calculation of a headingfrom an automatically determined wind correction angle by the use of aconstant bank angle to reduce repeated course corrections when a crosswind is not accounted for along a flight route.

2. Background

Wind is an environmental factor that may affect the flight of anaircraft. For example, a tailwind is a wind that blows in the directionof travel of the aircraft. A tailwind may increase the relative groundspeed of the aircraft and may reduce the total time required to reach adestination. In contrast, a headwind blows against the direction oftravel of an aircraft and may have the opposite effect.

Other types of winds also may affect the ground track for the flight ofan aircraft. A ground track is the path of the aircraft on the surfaceof the Earth directly below the aircraft. More specifically, a groundtrack may be the intended course or direction of travel over the surfaceof the Earth with respect to north. For example, a crosswind is aportion of the wind that may cause an aircraft to drift off course. Theheading is the direction in which the longitudinal axis of the aircraftis pointing in relation to magnetic north.

Adjustments may be made to the heading of the aircraft in response to acrosswind such that a course along an intended ground track ismaintained. These adjustments typically include having knowledge of thedirection and speed of the wind.

Typically, information about winds may be calculated from informationobtained through the use of a weather balloon. The information obtainedfrom the weather balloon may be used by a ground location, such as anair traffic control service. The weather balloon contains equipmentconfigured to record the position of the weather balloon at differentlocations. The weather balloon may also be configured to record otherinformation, such as speed and direction of the wind, as the weatherballoon travels through the atmosphere.

These weather balloons, however, may not provide as much information asdesired about the winds. For example, a weather balloon typically onlygives a vertical profile of winds. Additional weather balloons may beused to provide information about the wind in larger areas. This use ofweather balloons may be more expensive and time consuming than desired.Additionally, the use of weather balloons also may be less feasible overareas, such as those that are used as flight corridors for commercialaircraft. In the case of flight operations of unmanned aerial vehicles,course routing may occur over or within airspace in which informationabout the wind is not available.

Further, to receive information about the wind from a secondary source,the aircraft requires hardware configured to receive the informationfrom an air traffic control service. In the case of unmanned aerialvehicles, it may be prohibitive both in payload restrictions and payloadspace restrictions to install the necessary systems to receiveinformation about the wind to determine a course correction angle forthe wind.

Therefore, it would be desirable to have a method and apparatus thattakes into account some of the issues discussed above as well aspossibly other issues.

SUMMARY

In one illustrative embodiment, a method for operating an aircraft ispresent. The aircraft is flown at a constant bank angle in which theaircraft crosses an intended ground track for the aircraft. Informationis identified about a wind using positions of the aircraft flying at theconstant bank angle.

In another illustrative embodiment, a method for operating an unmannedaerial vehicle is present. The unmanned aerial vehicle is flown acrossan intended ground track at a constant bank angle. Positions of theunmanned aerial vehicle are identified while the unmanned aerial vehicleflies at the constant bank angle. A speed and a direction of a wind areidentified using the positions of the unmanned aerial vehicle and theconstant bank angle. The unmanned aerial vehicle is operated to fly onthe intended ground track using the speed and the direction of the wind.

In yet another illustrative embodiment, an aircraft management systemcomprises a computer system. The computer system is configured toreceive information about an aircraft flying along a maneuver groundtrack with a constant bank angle. The maneuver ground track crosses anintended ground track of the aircraft. The computer system is furtherconfigured to identify information about a wind from positions of theaircraft along the maneuver ground track.

The features and functions can be achieved independently in variousembodiments of the present disclosure or may be combined in yet otherembodiments in which further details can be seen with reference to thefollowing description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrativeembodiments are set forth in the appended claims. The illustrativeembodiments, however, as well as a preferred mode of use, furtherobjectives, and advantages thereof will best be understood by referenceto the following detailed description of an illustrative embodiment ofthe present disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an illustration of an aircraft environment in accordance withan illustrative embodiment;

FIG. 2 is an illustration of a maneuver that is performed by an aircraftto identify wind information in accordance with an illustrativeembodiment;

FIG. 3 is an illustration of a block diagram of an aircraft environmentin accordance with an illustrative embodiment;

FIG. 4 is an illustration of a data processing system in accordance withan illustrative embodiment;

FIG. 5 is an illustration of a flowchart of a process for operating anaircraft in accordance with an illustrative embodiment;

FIG. 6 is an illustration of a flowchart of a process for operating anaircraft using wind information in accordance with an illustrativeembodiment; and

FIG. 7 is an illustration of a flowchart of a process for operating anunmanned aerial vehicle in accordance with an illustrative embodiment.

DETAILED DESCRIPTION

The illustrative embodiments recognize and take into account one or moredifferent considerations. For example, the different illustrativeembodiments recognize and take into account that aircraft withoutequipment configured to identify a course correction angle taking intoaccount the wind; aircraft, such as unmanned aerial vehicles, may stillidentify information about the winds that allows the aircraft to beoperated in a desired manner.

The illustrative embodiments recognize and take into account that anaircraft may fly at a constant bank angle turn in circles. The deviationor drift from the center point of each circle flown by the aircraft maybe used to identify information about the wind. The illustrativeembodiments recognize and take into account that as the number ofdeviations increase from an intended ground track, such as those fromflying circles, the range of an unmanned aerial vehicle may be reducedin a manner making it more difficult to perform mission objectives.

The different illustrative embodiments recognize and take into accountthat this type of process, however, may use time and resources that maynot be applied to the mission of the aircraft. For example, flying incircles to identify wind in the vicinity of the aircraft may take timeand fuel that is otherwise used to fly the aircraft along a flight path.As a result, the aircraft may not have as long of a range as desired.

With reference now to the figures and, in particular, with reference toFIG. 1, an illustration of an aircraft environment is depicted inaccordance with an illustrative embodiment. Aircraft environment 100 isan example of an environment in which aircraft 102 may be operated. Inthis illustrative example, aircraft 102 may take the form of unmannedaerial vehicle (UAV) 104.

As depicted, aircraft 102 may be controlled from remote position 106 inthese illustrative examples. Remote position 106 may take various forms.For example, as depicted, remote position 106 may be a building, avehicle, an air traffic control tower, a ship, a ground station, or someother suitable position.

As depicted, aircraft 102 flies in the air at a selected heading suchthat the actual path of flight follows intended ground track 110. Inother words, desired course 108 following intended ground track 110 isthe result of flying in the direction of heading 107 related to wind 114resulting in wind correction angle 109. Wind correction angle 109 is theangle between desired course 108 when following intended ground track110 and heading 107 needed to fly on intended ground track 110 when wind114 is present.

In the illustrative examples, intended ground track 110 is a path onground 112 that is planned for aircraft 102. Intended ground track 110may be set, for example, without limitation, in a flight plan, by anoperator of aircraft 102, or some other suitable source.

Maintaining flight over intended ground track 110 may be desirable for anumber of different reasons. When used with reference to items, “anumber of” items means one or more items. For example, a number ofdifferent reasons is one or more different reasons.

One reason for maintaining flight over intended ground track 110 is thataircraft 102 may be performing surveillance of ground 112 along intendedground track 110. Deviation from intended ground track 110 may result inan inability to obtain information about ground 112 along intendedground track 110. More specifically, aircraft 102 may not be able totake pictures or video of target objects that may be on ground 112 ifaircraft 102 deviates far enough away from intended ground track 110. Inother cases, flying aircraft on intended ground track 110 may be part ofa plan to organize traffic to avoid aircraft from flying closer to eachother than desired.

In one illustrative example, maintaining flight of aircraft 102 alongintended ground track 110 may be performed in order to ensure thevehicle is always in the vicinity of friendly forces and away from knownenemy force locations. In this manner, aircraft 102 may be safelyrecovered in the event of an in-flight emergency requiring immediaterecovery of aircraft 102.

In these illustrative examples, wind 114 is an example of anenvironmental condition that may cause aircraft 102 to deviate fromintended ground track 110. With information about wind 114, aircraft 102may be operated to maintain flight along intended ground track 110. Wind114 may be a crosswind in these illustrative examples.

In these illustrative examples, aircraft 102 may be operated in a mannerthat identifies wind 114 that is present in the vicinity of aircraft102. Wind 114 is in the vicinity of aircraft 102 when wind 114 has thepotential to affect the flight of aircraft 102 over intended groundtrack 110.

The identification of information about wind 114 may be used to operateaircraft 102 or may be used by other aircraft, such as aircraft 116. Inthis illustrative example, aircraft 102 may directly transmit thisinformation to aircraft 116.

In other illustrative examples, aircraft 102 may transmit thisinformation to remote position 106. In turn, remote position 106 maytransmit this information to aircraft 116 or to some other aircraft inneed of information about wind 114.

In still other illustrative examples, if aircraft 116 is an unmannedaerial vehicle, aircraft 116 may also be controlled by an operator atremote position 106 or other remote positions. That operator may use theinformation about wind 114 to operate aircraft 116.

In these illustrative examples, aircraft 102 may be operated in a mannerthat does not cause aircraft 102 to deviate from intended ground track110 as much as using other techniques for identifying wind 114. In theseillustrative examples, true airspeed of aircraft 102 is the speed ofaircraft 102 relative to the air mass in which aircraft 102 flies.

Turning now to FIG. 2, an illustration of a maneuver performed by anaircraft to identify information about the wind is depicted inaccordance with an illustrative embodiment. In this illustrativeexample, aircraft 102 is in position 200 and flies along intended groundtrack 110. At some point, it may be desirable to determine whether wind114 is present in a manner that affects the flight of aircraft 102 onintended ground track 110.

Position 200 is a position of aircraft 102 relative to intended groundtrack 110. Position 200 may be measured using two-dimensionalcoordinates. In this illustrative example, x-axis 202 and y-axis 201define a plane relative to the surface of ground 112. In someillustrative examples, the coordinates may take the form of latitude andlongitude.

Aircraft 102 may deviate from intended ground track 110 to perform amaneuver relative to intended ground track 110. This maneuver may be fora short period of time such that the mission of aircraft 102 is affectedas little as possible or desired. The maneuver is performed to identifyinformation about wind 114.

In these illustrative examples, information about aircraft 102 isidentified while aircraft 102 performs the maneuver along maneuverground track 203. For example, without limitation, initial heading, trueairspeed, position, and bank angle are some types of information thatmay be identified for aircraft 102.

In this illustrative example, the maneuver performed by aircraft 102 maybe one or more banking maneuvers in which aircraft 102 turns with aconstant bank angle. The maneuver may include crossing intended groundtrack 110 on maneuver ground track 203. In these illustrative examples,aircraft 102 flying on maneuver ground track 203 crosses intended groundtrack 110 at a constant heading. In other words, aircraft 102 does notchange direction while aircraft 102 flies across intended ground track110 along maneuver ground track 203 at position 206. In thisillustrative example, the true airspeed heading is unknown but may besolved by using information about aircraft 102 that is identified whileaircraft 102 performs the maneuver.

For example, aircraft 102 may fly to a side of intended ground track110, as illustrated with aircraft 102 in position 205. From position205, aircraft 102 may fly across intended ground track 110 alongmaneuver ground track 203 to position 206. In the illustrative examples,this portion of the maneuver is flown with wings level. In other words,a bank angle of about zero is used.

As depicted, aircraft 102 flies across intended ground track 110 atposition 206 when following maneuver ground track 203. Constant bankangle is used by aircraft 102 when aircraft 102 reaches the vicinity ofposition 206. Maneuver ground track 203 is the ground track whichresults from the constant bank angle flown by aircraft 102 when making aturn in performing the maneuver.

A bank angle, in these illustrative examples, is an angle at whichaircraft 102 is inclined about longitudinal axis 208 for aircraft 102.Longitudinal axis 208 is an axis that extends centrally through aircraft102.

As depicted, angle 210 is an angle of maneuver ground track 203 foraircraft 102 relative to intended ground track 110. For example, theturn in the maneuver performed by aircraft 102 to fly along maneuverground track 203 may cross intended ground track 110 with angle 210being about 45 degrees. Of course, the crossing may be at other angles,depending on the particular implementation. Angle 210 may not be knownwith a precise value in the illustrative examples. The bank angle flownby aircraft 102 may be about five degrees in this illustrative example.

In a similar fashion, angle 212 also may be a constant angle whenaircraft 102 crosses intended ground track 110 at position 214. Angle212 may be the same or different from angle 210, depending on theparticular implementation.

Aircraft 102 may fly across intended ground track 110 at position 214with a second constant bank angle. This second constant bank angle maybe the same as the constant bank angle at which aircraft 102 fliesacross intended ground track 110 at position 206. In this example, thedirection of the turn with the constant bank angle is in the oppositedirection.

In these illustrative examples, the angle at which aircraft 102 crossesintended ground track 110 at position 206 is unknown but is related tothe initial heading for aircraft 102 in this maneuver. The initialheading is a piece of data that may be used to identify informationabout wind 114. The initial heading may be identified using a leastsquares procedure as described below.

In these illustrative examples, aircraft 102 identifies positions 216.Positions 216 are positioned on the ground that aircraft 102 identifieswhile flying on maneuver ground track 203. Positions 216 may be the sameor different from positions along maneuver ground track 203, dependingon the accuracy at which positions 216 are measured by aircraft 102.

Positions 216 may be identified in a number of different ways. Forexample, positions 216 may be identified using a location identificationsystem on board aircraft 102. The on board location system may be, forexample, a global positioning system receiver. Positions 216 arerecorded by aircraft 102 in these illustrative examples. Positions 216may not exactly track maneuver ground track 203, depending on theaccuracy of the location identification system. The amount of deviationof positions 216 from maneuver ground track 203 depends on the accuracyof the on board location system used in aircraft 102.

If wind 114 is absent, positions 216 may be the same as positions alongzero wind ground track 217. The presence of wind 114 may result in oneor more of positions 216 being different from corresponding positions onzero wind ground track 217. In other words, a position in positions 216may be different from a corresponding position along zero wind groundtrack 217 that was predicted for aircraft 102 without wind 114.

In these illustrative examples, positions 216, the constant bank angle,and the true airspeed of aircraft 102 may be used to identifyinformation about wind 114. This identified information about wind 114may include values for wind speed and wind direction. This process mayinclude a least squares analysis that identifies values for wind speedand wind direction as best values for these parameters.

With the identification of information about wind 114, the operation ofaircraft 102 may be adjusted such that aircraft 102 flies along intendedground track 110 in the presence of wind 114. In particular, heading 107of aircraft 102 may be adjusted such that aircraft 102 maintainsintended ground track 110. This adjustment may be made without the needfor repeated banking turn maneuvers to maintain intended ground track110.

Further, wind data calculated from the maneuver along maneuver groundtrack 203 may be used to operate aircraft 102 to still fly substantiallyalong intended ground track 110 as compared to other methods in whichaircraft 102 flies in circles. Further, with information about wind 114,the flight of other aircraft also may be adjusted such that thoseaircraft fly along an intended ground track when those aircraft are inthe vicinity of wind 114 that affects the flight of the other aircraft.

This type of maneuver may be especially useful when aircraft 102 takesthe form of unmanned aerial vehicle 104. The maneuver, theidentification of wind information, the identification of windcorrection angle 109 in FIG. 1, the adjustment of heading 107, or somecombination thereof may be performed automatically by unmanned aerialvehicle 104. In other words, a remote operator of unmanned aerialvehicle 104 does not need to perform these tasks to maintain the flightof unmanned aerial vehicle 104 over intended ground track 110.

Turning now to FIG. 3, an illustration of a block diagram of an aircraftenvironment is depicted in accordance with an illustrative embodiment.In this illustrative example, aircraft environment 100 in FIG. 1 is anexample of one implementation for aircraft environment 300.

As depicted, number of aircraft 302 operates within aircraft environment300. In this illustrative example, aircraft 304 within number ofaircraft 302 may fly on intended ground track 306. In these illustrativeexamples, wind 308 may affect the operation of aircraft 304 with respectto intended ground track 306.

In these illustrative examples, wind identifier 310 is used to identifyinformation 312 about wind 308. In these illustrative examples,information 312 may take the form of wind vector 314. Wind vector 314may include speed 316 of wind 308 and direction 318 of wind 308.

In these illustrative examples, wind identifier 310 may be implementedin hardware, software, or a combination of the two. In theseillustrative examples, wind identifier 310 may be implemented withincomputer system 320. In these illustrative examples, wind identifier 310is located in aircraft 304.

As depicted, aircraft 304 generates information 322 during flight thatis used by wind identifier 310 to identify information 312 about wind308. In particular, information 322 may be generated during maneuver324. Maneuver 324 may be a maneuver that deviates from intended groundtrack 306 and is performed relative to intended ground track 306.

As depicted, information 322 is generated using sensor system 326 inaircraft 304. Sensor system 326 may include a location system. Thislocation system may be, for example, an inertial measurement unit, aglobal positioning system receiver, an airspeed indicator, an altimeter,an attitude sensor, an outside air temperature probe, and other suitabletypes of systems that are configured to generate information aboutpositions for aircraft 304.

In these illustrative examples, information 322 may include speed 328 ofaircraft 304, bank angle 329 for aircraft 304, and measured positions330 of aircraft 304 during the performance of maneuver 324. The bankangle may be identified from information generated by an attitudesensor.

Additionally, computer system 320 may identify true airspeed 331 usinginformation 322. Examples of information 322 that may be used toidentify true airspeed 331 include, for example, indicated airspeed fromthe airspeed calibration data, the compressibility correction, and airdensity. Airspeed calibration data is the correction from indicatedairspeed to calibrated airspeed. The compressibility correction is thecorrection from calibrated to equivalent airspeed. This correction isnegligible at low subsonic speeds. Air density is calculated frompressure altitude and outside air temperature.

In these illustrative examples, maneuver 324 takes the form of number ofturns 332. For example, first turn 333 in number of turns 332 isperformed with first constant bank angle 334. In other words, the bankangle of aircraft 304 is substantially the same during first turn 333 inthese illustrative examples.

Number of turns 332 in maneuver 324 also may include second turn 336.Second turn 336 is performed using second constant bank angle 338. Firstconstant bank angle 334 and second constant bank angle 338 may be thesame magnitude but in opposite directions, depending on the particularimplementation.

First turn 333 is on maneuver ground track 344 and crosses intendedground track 306. Maneuver ground track 344 is comprised of positions352. Second turn 336 is also on maneuver ground track 344 and alsoresults in aircraft 304 crossing intended ground track 306 a second timein these illustrative examples. In these illustrative examples, zerowind ground track 354 comprises positions 356 for aircraft 304 thataircraft 304 should fly over during the performance of maneuver 324 ifaircraft 304 is unaffected by wind 308.

In these illustrative examples, information 322 generated by aircraft304 includes generating information 322 at pre-determined intervals. Inthese illustrative examples, number of turns 332 in maneuver 324 mayonly include first turn 333 but not second turn 336, depending on theparticular implementation. Information 322 generated from first turn 333may provide sufficient amounts of information 322 to identifyinformation 312 about wind 308. In yet other illustrative examples,additional turns may be present in addition to first turn 333 and secondturn 336.

In these illustrative examples, first turn 333 and second turn 336 arein opposite directions to each other relative to intended ground track306. First constant bank angle 334 and second constant bank angle 338may be, for example, about 10 degrees, five degrees, or some othersuitable value.

In identifying information 312 about wind 308, measured positions 330for aircraft 304 when flying along maneuver ground track 344 shouldmatch positions 356 for zero wind ground track 354 if wind 308 does notaffect the operation of aircraft 304. If a deviation is present betweenany of measured positions 330 and maneuver ground track 344, wind 308has a sufficient force to affect the operation of aircraft 304 while itflies within aircraft environment 300.

In these illustrative examples, theoretical positions are positions inpositions 352 of aircraft 304 flying along maneuver ground track 344. Inidentifying information 312 about wind 308, the theoretical position foraircraft 304 can be calculated by wind identifier 310 using thefollowing equations:

$\begin{matrix}{\frac{x}{t} = {{v \cdot {\cos \left( A_{z} \right)}} + v_{{wind},x}}} & (1) \\{\frac{y}{t} = {{v \cdot {\sin \left( A_{z} \right)}} + v_{{wind},y}}} & (2)\end{matrix}$

where A_(z) is the true airspeed heading of aircraft 304 at any time t.In the illustrative examples, the speed of aircraft 304 may becharacterized in a number of different ways. For example, the speed ofaircraft 304 may be described using indicated airspeed, true airspeed,and ground speed. The heading for each of these speeds is a compassdirection of the aircraft for the particular type of speed. For example,indicated airspeed and true airspeed have the same direction butdifferent magnitudes. Ground speed is the speed of the airplane alongthe ground and, due to wind effects, may have a different direction anda different magnitude compared to the indicated and true airspeeds.

At any point along the bank maneuver, A_(z)=A_(z.int)+A_(z.t). In theseillustrative examples, the time t is measured relative to when the bankmaneuver begins. For example, the maneuver may begin at the time atwhich aircraft 304 first crosses intended ground track 306. Directionsof the x and y coordinates are arbitrary. The true heading angle rate,Q, may be calculated using the following equation:

$\begin{matrix}{Q = \frac{g \cdot {\tan (\phi)}}{v_{T}}} & (3)\end{matrix}$

where

$Q:=\frac{A_{z}}{t}$

and Q is the true heading angle rate degrees/sec, g=32.2 ft/s², φ=bankangle degrees, and ν_(T)=true speed (ft/s).

Integrating equations 1 and 2 result in the following equations:

$\begin{matrix}{{{fx}\left( {A_{z\; 0},v_{{wind},x},j} \right)}:={x_{j} - {\frac{v_{T}}{Q} \cdot {\sin \left( {A_{z\; 0} + {Q \cdot {time}_{j}}} \right)}} - {v_{{wind},x} \cdot {time}_{j}} - \left( {x_{1} - {\frac{v_{T}}{Q} \cdot {\sin \left( A_{z\; 0} \right)}}} \right)}} & (4) \\{{{fy}\left( {A_{z\; 0},v_{{wind},y},j} \right)}:={y_{j} - y_{1} + {\frac{v_{T}}{Q} \cdot {\cos \left( {A_{z\; 0} + {Q \cdot {time}_{j}}} \right)}} - {v_{{wind},y} \cdot {time}_{j}} - {\frac{v_{T}}{Q} \cdot {\cos \left( A_{z\; 0} \right)}}}} & (5)\end{matrix}$

In these illustrative examples, time_(j) is time measured from the startof the turn using the constant bank angle. Squaring and summingequations (4) and (5) over all measured positions 330 and taking thederivatives with respect to A_(z) provides:

$\begin{matrix}{{\frac{{fx}}{A_{z}}\left( {A_{z\; 0},v_{{wind},x}} \right)}:={\sum\limits_{j = 1}^{J\max}\left\lbrack {{{fx}\left( {A_{z\; 0},v_{{wind},x},j} \right)} \cdot \left( {{- {\cos \left( {A_{z\; 0} + {Q\; \cdot {time}_{j}}} \right)}} + {\cos \left( A_{z\; 0} \right)}} \right)} \right\rbrack}} & (6) \\{{\frac{{fy}}{A_{z}}\left( {A_{z\; 0},v_{{wind},y}} \right)}:={\sum\limits_{j = 1}^{J\max}{\left\lbrack {{{fy}\left( {A_{z\; 0},v_{{wind},y},j} \right)} \cdot \left( {{- {\sin \left( {A_{z\; 0} + {Q\; \cdot {time}_{j}}} \right)}} + {\sin \left( A_{z\; 0} \right)}} \right)} \right\rbrack.}}} & (7)\end{matrix}$

Squaring and summing equations (4) and (5) over all measured positions330 and taking the derivatives with respect to ν_(wind.x) and ν_(wind.y)provides:

$\begin{matrix}{{\frac{{fx}}{v_{{wind},x}}\left( {A_{z\; 0},v_{{wind},x}} \right)}:={\sum\limits_{j = 1}^{J\; \max}\left\lbrack {{{fx}\left( {A_{z\; 0},v_{{wind},x},j} \right)} \cdot \left( {- {time}_{j}} \right)} \right\rbrack}} & (8) \\{{\frac{{fy}}{v_{{wind},y}}\left( {A_{z\; 0},v_{{wind},y}} \right)}:={\sum\limits_{j = 1}^{J\; \max}{\left\lbrack {{{fy}\left( {A_{z\; 0},v_{{wind},y},j} \right)} \cdot \left( {- {time}_{j}} \right)} \right\rbrack.}}} & (9)\end{matrix}$

Adding equations 6 and 7 and using equations 8 and 9 results in thefollowing equations:

$\begin{matrix}{{{\frac{{fx}}{A_{z}}\left( {A_{z\; 0},v_{{wind},x}} \right)} + {\frac{{fx}}{A_{z}}\left( {A_{z\; 0},v_{{wind},y}} \right)}} = 0} & (10) \\{{\frac{{fx}}{v_{{wind},x}}\left( {A_{z\; 0},v_{{wind},x}} \right)} = 0} & (11) \\{{\frac{{fy}}{v_{{wind},y}}\left( {A_{z\; 0},v_{{wind},y}} \right)} = 0.} & (12)\end{matrix}$

Equations 10, 11, and 12 are solved for Az0, ν_(wind.x), and ν_(wind.y).Measured positions 330 measured during maneuver 324 are used in theequations for x and y, and a least squares analysis is performed on allof measured positions 330. This least squares analysis determines thebest values for the three unknowns, initial true airspeed heading,ν_(wind.x) and ν_(wind.y), by minimizing the differences between themeasured position and the theoretical position. In these illustrativeexamples, the initial true airspeed heading is the same heading thataircraft 304 is flying when aircraft 304 crosses intended ground track306 while performing maneuver 324. Wind speed and wind direction can bedetermined from ν_(wind.x) and ν_(wind.y). The measured position is aposition in measured positions 330 as identified by aircraft 304.

In this manner, wind identifier 310 may use true airspeed 331, bankangle 329, and measured positions 330 recorded during maneuver 324. Noother information is needed in the illustrative examples.

In this manner, wind identifier 310 identifies information 312 aboutwind 308, such as speed 316 and direction 318. This information aboutwind 308 may be used to operate aircraft 304 to follow intended groundtrack 306 now that information 312 about wind 308 has been identified.

Further, maneuver 324 may be performed a number of different times whileaircraft 304 travels along intended ground track 306. Additionally,aircraft 304 may transmit information 312 to other aircraft in number ofaircraft 302. For example, aircraft 304 may transmit this informationdirectly to other aircraft in number of aircraft 302. In otherillustrative examples, information 312 may be transmitted to remotelocation 347. In turn, remote location 347 may send information 312 toother aircraft in number of aircraft 302.

Turning now to FIG. 4, an illustration of a data processing system isdepicted in accordance with an illustrative embodiment. Data processingsystem 400 may be used to implemented one or more computers in computersystem 320 in FIG. 3. In this illustrative example, data processingsystem 400 includes communications framework 402, which providescommunications between processor unit 404, memory 406, persistentstorage 408, communications unit 410, input/output (I/O) unit 412, anddisplay 414. In this example, communications framework 402 may take theform of a bus system.

Processor unit 404 serves to execute instructions for software that maybe loaded into memory 406. Processor unit 404 may be a number ofprocessors, a multi-processor core, or some other type of processor,depending on the particular implementation. Further, in someillustrative examples, wind identifier 310 in FIG. 3 may be implementedusing hardware, such as processor unit 404.

Memory 406 and persistent storage 408 are examples of storage devices416. A storage device is any piece of hardware that is capable ofstoring information, such as, for example, without limitation, data,program code in functional form, and/or other suitable informationeither on a temporary basis and/or a permanent basis. Storage devices416 may also be referred to as computer readable storage devices inthese illustrative examples. Memory 406, in these examples, may be, forexample, a random access memory or any other suitable volatile ornon-volatile storage device. Persistent storage 408 may take variousforms, depending on the particular implementation.

For example, persistent storage 408 may contain one or more componentsor devices. For example, persistent storage 408 may be a hard drive, aflash memory, a rewritable optical disk, a rewritable magnetic tape, orsome combination of the above. The media used by persistent storage 408also may be removable. For example, a removable hard drive may be usedfor persistent storage 408.

Communications unit 410, in these illustrative examples, provides forcommunications with other data processing systems or devices. In theseillustrative examples, communications unit 410 is a network interfacecard.

Input/output unit 412 allows for input and output of data with otherdevices that may be connected to data processing system 400. Forexample, input/output unit 412 may provide a connection for user inputthrough a keyboard, a mouse, and/or some other suitable input device.Further, input/output unit 412 may send output to a printer. Display 414provides a mechanism to display information to a user.

Instructions for the operating system, applications, and/or programs maybe located in storage devices 416, which are in communication withprocessor unit 404 through communications framework 402. The processesof the different embodiments may be performed by processor unit 404using computer-implemented instructions, which may be located in amemory, such as memory 406.

These instructions are referred to as program code, computer usableprogram code, or computer readable program code that may be read andexecuted by a processor in processor unit 404. The program code in thedifferent embodiments may be embodied on different physical or computerreadable storage media, such as memory 406 or persistent storage 408.

Program code 418 is located in a functional form on computer readablemedia 420 that is selectively removable and may be loaded onto ortransferred to data processing system 400 for execution by processorunit 404. Program code 418 and computer readable media 420 form computerprogram product 422 in these illustrative examples. In one example,computer readable media 420 may be computer readable storage media 424or computer readable signal media 426.

In these illustrative examples, computer readable storage media 424 is aphysical or tangible storage device used to store program code 418rather than a medium that propagates or transmits program code 418.Alternatively, program code 418 may be transferred to data processingsystem 400 using computer readable signal media 426. Computer readablesignal media 426 may be, for example, a propagated data signalcontaining program code 418. For example, computer readable signal media426 may be an electromagnetic signal, an optical signal, and/or anyother suitable type of signal. These signals may be transmitted overcommunications links, such as wireless communications links, opticalfiber cable, coaxial cable, a wire, and/or any other suitable type ofcommunications link.

The different components illustrated for data processing system 400 arenot meant to provide architectural limitations to the manner in whichdifferent embodiments may be implemented. The different illustrativeembodiments may be implemented in a data processing system includingcomponents in addition to and/or in place of those illustrated for dataprocessing system 400. Other components shown in FIG. 4 can be variedfrom the illustrative examples shown. The different embodiments may beimplemented using any hardware device or system capable of runningprogram code 418.

The illustration of aircraft environment 300 in FIG. 3 and dataprocessing system 400 in FIG. 4 are not meant to imply physical orarchitectural limitations to the manner in which an illustrativeembodiment may be implemented. Other components in addition to or inplace of the ones illustrated may be used. Some components may beunnecessary. Also, the blocks are presented to illustrate somefunctional components. One or more of these blocks may be combined,divided, or combined and divided into different blocks when implementedin an illustrative embodiment.

For example, wind identifier 310 may be located at remote location 347rather than in aircraft 304. For example, wind identifier 310 may beimplemented in a computer system or other hardware in remote location347 that may be a platform, such as, for example, a building, anotheraircraft, a ship, or some other suitable remote location. Further,aircraft 304 may take a number of different forms. For example, aircraft304 may be an airplane, a helicopter, an unmanned aerial vehicle, orsome other suitable type of aircraft.

As another example, hardware for wind identifier 310 may be implementedusing other types of hardware other than computer system 320. Forexample, the hardware may take the form of a circuit system, anintegrated circuit, an application specific integrated circuit (ASIC), aprogrammable logic device, or some other suitable type of hardwareconfigured to perform a number of operations.

With a programmable logic device, the device is configured to performthe number of operations. The device may be reconfigured at a later timeor may be permanently configured to perform the number of operations.Examples of programmable logic devices include, for example, aprogrammable logic array, a programmable array logic, a fieldprogrammable logic array, a field programmable gate array, and othersuitable hardware devices. Additionally, the processes may beimplemented in organic components integrated with inorganic componentsand/or may be comprised entirely of organic components excluding a humanbeing.

The different components illustrated in FIGS. 1 and 2 may be combinedwith components in FIG. 3, used with components in FIG. 3, or acombination of the two. Additionally, some of the components illustratedin FIGS. 1 and 2 may be illustrative examples of how components shown inblock form in FIGS. 3 and 4 may be implemented as physical components.

With reference now to FIG. 5, an illustration of a flowchart of aprocess for operating an aircraft is depicted in accordance with anillustrative embodiment. The process illustrated in FIG. 5 may beimplemented in aircraft environment 100 in FIG. 1 or aircraftenvironment 300 in FIG. 3.

In this illustrative example, the process may turn an aircraft to fly toa side of an intended ground track for the aircraft (operation 500).Thereafter, the aircraft turns to fly along a maneuver ground track at aconstant heading in which the maneuver ground track crosses the intendedground track of the aircraft (operation 502). The constant bank anglefor the maneuver is initiated at this point. Flying to one side of theintended ground track and then flying a constant heading back towardsthe intended ground track at true airspeed heading Az0 is a part of themaneuver in these illustrative examples.

The process then collects information about the aircraft while theaircraft turns to fly along the maneuver ground track at the constantbank angle (operation 504). This information may include, for example,positions of the aircraft, speed of the aircraft, and other suitableinformation. The process then identifies a wind vector for wind from thepositions of the aircraft relative to the maneuver ground track(operation 506). Operation 506 also may include using other informationabout the aircraft.

For example, other information, such as the bank angle, the positionsrecorded for the aircraft, the true airspeed calculated for theaircraft, and other suitable information, may be used with respect tothe equations described above. Information, such as initial trueairspeed heading of the aircraft when the aircraft crosses the intendedground track and wind information, may be identified using the equationsdescribed above.

The process then operates the aircraft using the wind information(operation 508), with the process terminating thereafter. In operation508, adjustments may be made to the aircraft such that the aircraftflies along the intended ground track. These adjustments may include,for example, changes in control surface configurations, thrust, andother suitable adjustments. In this manner, the aircraft may be operatedto fly more closely along an intended ground track.

With reference now to FIG. 6, an illustration of a flowchart of aprocess for operating an aircraft using wind information is depicted inaccordance with an illustrative embodiment. The process illustrated inFIG. 6 is one example of operations that may be performed for operation508 in FIG. 5.

The process begins by identifying a wind correction angle using the windinformation (operation 600). The process then adjusts a heading of theaircraft such that the aircraft flies on the intended ground track(operation 602), with the process terminating thereafter.

In these illustrative examples, the process in FIG. 6 may be performedautomatically by the aircraft. The operations in FIGS. 5 and 6 may beperformed in a number of different ways. For example, these operationsmay be performed automatically by a computer system for the aircraft.This computer system may be located in the aircraft or in an orientedremote location. In the illustrative examples, performing an operationautomatically, means that the operation may be performed without needinguser input to initiate performance of the operation.

Turning now to FIG. 7, an illustration of a flowchart of a process foroperating an unmanned aerial vehicle is depicted in accordance with anillustrative embodiment. This process may be implemented in an unmannedaerial vehicle, such as unmanned aerial vehicle 104 in FIG. 1. Thedifferent operations may be performed automatically without requiringuser input.

The process begins by maneuvering the unmanned aerial vehicle to crossan intended ground track at a constant heading (operation 700). In theillustrative examples, the intended ground track is crossed with a bankangle of about zero. In other words, the intended ground track iscrossed with the wings of the unmanned aerial vehicle being level inthese illustrative examples.

Thereafter, the unmanned aerial vehicle enters into a turn and maintainsa constant bank angle in the turn (operation 702). This turn results inthe unmanned aerial vehicle crossing the intended ground track.

Positions of the unmanned aerial vehicle are measured and recordedduring the performance of the maneuver (operation 704). The unmannedaerial vehicle then identifies information about the wind using the trueairspeed, the bank angle, and the positions recorded during the maneuver(operation 706). The wind information includes a speed of the wind and adirection of the wind. In other words, this wind information may be avector of the wind encountered by the unmanned aerial vehicle.

The unmanned aerial vehicle identifies a wind correction angle based onthe wind information (operation 708). A heading is then identified usingthe correction angle (operation 710). In the illustrative examples, thisheading is a heading for the true airspeed of the unmanned aerialvehicle. This heading may be referred to as a wind correction courseheading. The unmanned aerial vehicle then flies using the heading suchthat the unmanned aerial vehicle substantially maintains flight on theintended ground track (operation 712), with the process terminatingthereafter.

The flowcharts and block diagrams in the different depicted embodimentsillustrate the architecture, functionality, and operation of somepossible implementations of apparatuses and methods in an illustrativeembodiment. In this regard, each block in the flowcharts or blockdiagrams may represent a module, segment, function, and/or a portion ofan operation or step. For example, one or more of the blocks may beimplemented as program code, in hardware, or a combination of theprogram code and hardware. When implemented in hardware, the hardwaremay, for example, take the form of integrated circuits that aremanufactured or configured to perform one or more operations in theflowcharts or block diagrams.

For example, operation 508 may be replaced by an operation in which theinformation about the wind is transmitted to another aircraft for use.This second aircraft may be in the vicinity of the aircraft used toidentify the information about the wind. This process also may berepeated periodically or along different portions of an intended groundtrack.

Thus, the different illustrative embodiments provide a method andapparatus for operating an aircraft. The different illustrativeembodiments provide an ability to identify information about wind thatmay affect the flight of an aircraft along an intended ground track.

One or more of the illustrative embodiments allow for an identificationof wind information for an aircraft without using other mechanisms, suchas weather balloons. Further, the information identified about the windsmay be more accurate than using other mechanisms, such as weatherballoons. In the illustrative examples, the effect of the wind on theaircraft performing maneuvers is used to identify information about thewinds that actually affect the flight of the aircraft.

Also, one or more illustrative embodiments do not involve transmittinginformation between the aircraft and an air traffic control service. Inthis manner, additional equipment may not be needed to identifyinformation about winds in operating the aircraft. As a result, lessweight, expense, and complexity may be present in an aircraft.

In some alternative implementations of an illustrative embodiment, thefunction or functions noted in the blocks may occur out of the ordernoted in the figures. For example, in some cases, two blocks shown insuccession may be executed substantially concurrently, or the blocks maysometimes be performed in the reverse order, depending upon thefunctionality involved. Also, other blocks may be added in addition tothe illustrated blocks in a flowchart or block diagram.

Thus, one or more illustrative embodiments provide a method andapparatus for identifying information about wind that may affect theflight of an aircraft over a ground track. In particular, one or moreillustrative embodiments may be applied to operating unmanned aerialvehicles.

In the illustrative examples, with the information identified about thewind, an automatic calculation of a heading from an automaticallydetermined wind correction angle by the use of a constant bank angle maybe used to reduce repeated course corrections when a cross wind is notaccounted for along a route of flight.

The description of the different illustrative embodiments has beenpresented for purposes of illustration and description and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different illustrativeembodiments may provide different features as compared to otherillustrative embodiments. The embodiment or embodiments selected arechosen and described in order to best explain the principles of theembodiments, the practical application, and to enable others of ordinaryskill in the art to understand the disclosure for various embodimentswith various modifications as are suited to the particular usecontemplated.

1. A method for operating an unmanned aerial vehicle, the methodcomprising: flying the unmanned aerial vehicle at a constant bank anglein which the unmanned aerial vehicle crosses an intended ground trackfor the unmanned aerial vehicle; identifying information about a windusing positions of the unmanned aerial vehicle flying at the constantbank angle; and adjusting flight of the unmanned aerial vehicle to flyon the intended ground track based on the wind identified by identifyinga wind correction angle using the information about the wind identifiedand adjusting a heading of the unmanned aerial vehicle such that theunmanned aerial vehicle flies on the intended ground track.
 2. Themethod of claim 1, wherein the steps of flying the unmanned aerialvehicle at the constant bank angle in which the unmanned aerial vehiclecrosses the intended ground track for the unmanned aerial vehicle;identifying the information about the wind using the positions of theunmanned aerial vehicle flying at the constant bank angle; and adjustingthe flight of the unmanned aerial vehicle to fly on the intended groundtrack based on the wind identified are performed automatically by acomputer system for the unmanned aerial vehicle.
 3. The method of claim1, wherein flying the unmanned aerial vehicle at the constant bank anglein which the unmanned aerial vehicle crosses the intended ground trackfor the unmanned aerial vehicle comprises: flying the unmanned aerialvehicle along a maneuver ground track at the constant bank angle acrossthe intended ground track of the unmanned aerial vehicle.
 4. The methodof claim 1, wherein flying the unmanned aerial vehicle at the constantbank angle in which the unmanned aerial vehicle crosses the intendedground track for the unmanned aerial vehicle comprises: flying theunmanned aerial vehicle in a turn with the constant bank angle in whichthe unmanned aerial vehicle crosses the intended ground track for theunmanned aerial vehicle.
 5. The method of claim 1, wherein the constantbank angle is a first constant bank angle and wherein flying theunmanned aerial vehicle at the constant bank angle in which the unmannedaerial vehicle crosses the intended ground track for the unmanned aerialvehicle comprises: flying the unmanned aerial vehicle in a first turn atthe first constant bank angle in which the unmanned aerial vehiclecrosses the intended ground track for the unmanned aerial vehicle, andfurther comprising: flying the unmanned aerial vehicle in a second turnat a second constant bank angle in which the unmanned aerial vehiclecrosses the intended ground track for the unmanned aerial vehicle froman opposite direction of the intended ground track.
 6. The method ofclaim 5, wherein identifying the information about the wind using thepositions of the unmanned aerial vehicle flying at the constant bankangle comprises: identifying the information about the wind using thepositions of the unmanned aerial vehicle flying at the first constantbank angle and the second constant bank angle.
 7. The method of claim 1further comprising: recording the positions of the unmanned aerialvehicle while the unmanned aerial vehicle flies at the constant bankangle.
 8. The method of claim 1 further comprising: identifying a trueairspeed for the unmanned aerial vehicle when crossing the intendedground track and wherein identifying the information about the windusing the positions of the unmanned aerial vehicle flying at theconstant bank angle comprises: identifying the information about thewind using the positions, the constant bank angle, and the true airspeedof the unmanned aerial vehicle.
 9. The method of claim 1, whereinidentifying the information about the wind comprises: identifying a windvector.
 10. A method for operating an unmanned aerial vehicle, themethod comprising: flying the unmanned aerial vehicle across an intendedground track at a constant bank angle; identifying positions of theunmanned aerial vehicle while the unmanned aerial vehicle flies at theconstant bank angle; identifying a speed and a direction of a wind usingthe positions of the unmanned aerial vehicle and the constant bankangle; and operating the unmanned aerial vehicle to fly on the intendedground track using the speed and the direction of the wind.
 11. Themethod of claim 10 further comprising: identifying a true airspeed ofthe unmanned aerial vehicle using the positions of the unmanned aerialvehicle and wherein identifying the speed and the direction of the windusing the positions of the unmanned aerial vehicle and the constant bankangle comprises: identifying the speed and the direction of the windusing the positions of the unmanned aerial vehicle, the constant bankangle, and the true airspeed of the unmanned aerial vehicle.
 12. Themethod of claim 10, wherein operating the unmanned aerial vehicle to flyon the intended ground track using the speed and the direction of thewind comprises: identifying a wind correction angle using the speed andthe direction of the wind; and adjusting a heading of the unmannedaerial vehicle such that the unmanned aerial vehicle flies on theintended ground track.
 13. An aircraft management system comprising: acomputer system configured to receive information about an aircraftflying along a maneuver ground track with a constant bank angle in whichthe maneuver ground track crosses an intended ground track of theaircraft and identify information about a wind from positions of theaircraft along the maneuver ground track.
 14. The aircraft managementsystem of claim 13, wherein the computer system is further configured toadjust flight of the aircraft to fly on the intended ground track basedon the wind identified.
 15. The aircraft management system of claim 14,wherein the aircraft is an unmanned aerial vehicle and wherein in beingconfigured to adjust the flight of the aircraft to fly on the intendedground track based on the wind identified, the computer system isconfigured to identify a wind correction angle using the windinformation identified; and adjust a heading of the unmanned aerialvehicle such that the unmanned aerial vehicle flies on the intendedground track.
 16. The aircraft management system of claim 13, whereinthe computer system is configured to automatically receive informationabout an aircraft flying along the intended ground track with theconstant bank angle in which the maneuver ground track crosses theintended ground track of the aircraft and identify the information aboutthe wind from the positions of the aircraft along the maneuver groundtrack.
 17. The aircraft management system of claim 13, wherein theaircraft flies in a turn at the constant bank angle in which theaircraft crosses the intended ground track for the aircraft.
 18. Theaircraft management system of claim 13, wherein the aircraft is anunmanned aerial vehicle.
 19. The aircraft management system of claim 13,wherein the computer system is located in at least one of the aircraftand a remote location.
 20. The aircraft management system of claim 13,wherein the information about the wind comprises a wind vector.